diff --git a/lib/internal/cluster/master.js b/lib/internal/cluster/master.js
index 8e4f9395da6..457b3579b12 100644
--- a/lib/internal/cluster/master.js
+++ b/lib/internal/cluster/master.js
@@ -275,12 +275,8 @@ function queryServer(worker, message) {
   if (worker.exitedAfterDisconnect)
     return;
 
-  const args = [message.address,
-                message.port,
-                message.addressType,
-                message.fd,
-                message.index];
-  const key = args.join(':');
+  const key = `${message.address}:${message.port}:${message.addressType}:` +
+              `${message.fd}:${message.index}`;
   var handle = handles[key];
 
   if (handle === undefined) {